The present invention claims priority from Japanese Patent Application No.9-22614 filed Feb. 2, 1997, the content of this being incorporated herein by reference.
1. Field of the Invention
The present invention relates to a multi-point video conference system and, particularly, to a privacy communication between specific points in a multi-point video conference.
2. Description of the Related Art
In a multi-point video conference system in which multi point video conference devices or terminals located in a plurality of points are connected to a multi-point control device through transmission paths and images of attendance of a conference at various points, that is, users of the multi-point video conference terminals, are displayed and their voices are output, in other multi-point video conference terminals, a privacy communication function for realizing a conversation between only specific points has been required.
In a conventional multi-point video conference system such as disclosed in, for example, Japanese Patent Application Laid-open No. H2-228158, a privacy communication function is realized by providing a controller in each video conference terminal for selecting at least two of multi-point video conference terminals which demand a privacy communication, a control signal processor in a video conference communication control unit, that is, multi-point control unit, for recognizing the video conference terminals demanding a mutual privacy communication and providing an information of the video conference terminals and an audio path controller in the multi-point control unit for controlling an audio path on the basis of the terminal information.
Such conventional multi-point video conference system will be described with reference to FIGS. 1, 2 and 3.
FIG. 1 is a block diagram showing a whole construction of such conventional multi-point video conference system.
The multi-point video conference system shown in FIG. 1 is constructed with a video conference communication controller 101, that is, a multi-point control unit and a plurality of multi-point video conference terminals 102, 103, 104 and 105 connected to the video conference communication controller 101 through bi-directional digital transmission paths 106, 107, 108 and 109, respectively.
The respective video conference terminals 102, 103, 104 and 105 are located in different points, send images and voices of attendance of a video conference through the bi-directional digital transmission paths and simultaneously receive the images and voices of other video conference terminals from the video conference communication controller 101 and display the images and output the voices thereof.
FIG. 2 is a block diagram showing a construction of the video conference terminal 102 of the multi-point video conference system shown in FIG. 1. Since the other video conference terminals 103, 104 and 105 have the same constructions as that of the video conference terminal 102, respectively, only the video conference terminal 102 will be described.
The video conference terminal 102 shown in FIG. 2 is constructed with an interface unit 110 connected to a bi-directional digital transmission path 106 for transmitting and receiving a signal, a signal processor 111 for multiplexing and processing an image of a user (input video signal), a voice (input audio signal) of the user and audio control signal, etc., a microphone 112 for input of a voice of an attendance of the conference, a loud-speaker 113 for output of voices of other conference attendance, a video camera 114 for input of the user image, a display 115 for output of the image of a talker in the video conference, a controller 116 for output of an audio control signal instructing a destination of the privacy communication and an echo canceler 117 for preventing an echo phenomenon from occurring due to an input of a voice from the loud-speaker 113 to the microphone 112.
In the video conference terminal 102 constructed as mentioned above, the audio signal, the video signal and the audio control signal from the microphone 112, the camera 114 and the controller 116 are multiplexed by the signal processor 111 and a resultant signal is sent from the interface unit 110 to the video conference communication controller 101 through the bi-directional digital transmission path 106.
On the other hand, the video conference communication controller 101 synthesizes an output video signal triggered by the audio signals transmitted from the respective video conference terminals 102, 103, 104 and 105 and synthesizes an output audio signal by summing the audio signals, as to be described later.
FIG. 3 shows a construction of the video conference communication controller 101 in the conventional multi-point video conference system disclosed in Japanese Patent Application Laid-open No. H2-228158.
The bi-directional digital transmission paths 106, 107, 108 and 109 and signal separators 118, 119, 120 and 121 connected to the respective bi-directional digital transmission paths receive the multiplexed signal from the respective video conference terminals 102, 103, 104 and 105, separate it to the input video signal, the input audio signal and the audio control signal and output them.
The input video signal among them is input to a video path unit 127 through an input video signal line 126 and the input audio signal is input to an audio level detector 133 and an audio path unit 124 through an input audio signal line 122. Further, the audio control signal is input to a control signal processor 130 through an audio control signal line 129.
An output of the audio path unit 124 and an output of the video path unit 127 are a input to the signal separators 118 to 121 through an output audio signal line 125 and an output video signal line 128, respectively. The respective signal separator units 118 to 121 multiplex these signals and send a resultant signal to the bi-directional digital transmission paths 106 to 109.
The control signal processor 130 functions to output an instruction assigning video conference terminals between which the audio privacy communication is to be performed, on the basis of the audio control signal output from the controller 116 of the video conference communication controller 101. An audio path control unit 131 controls the audio path unit 124 on the basis of the instruction output from the control signal processor 130 such that a content of the privacy communication is not output to other video conference terminals which are not objects of the privacy communication.
The audio level detector 123 detects one of the video conference terminals whose audio level is the highest. A video control unit 132 controls the video path unit 127 such that, among the video signals collected by the video path unit 127 through the input video signal line 125 from the respective terminals, a video signal of the video conference terminal 102 whose audio level is detected by the audio level detector 123 as the highest is output to the output video signal line 128. In this case, the output of the control signal processor 130 is also input to the audio level detector 123 to prevent the image in the privacy communication from being output.
A basic operation of the conventional multi-point video conference system constructed with the above mentioned multi-point video conference terminals and the video conference communication control unit (multi-point control unit) is as follow:
The video conference terminal 102 shown in FIG. 2 multiplexes the input video signal, the input audio signal and the audio control signal from the camera 114, the microphone 112 and the controller 116 and sends the resultant signal to the video conference communication controller 101 through the bi-directional digital transmission path 106.
The video conference communication controller 101 (FIG. 3) receives the multiplexed input signals from the respective video conference terminals 102 to 105 separates to the input video signals, the input audio signals and the audio control signals in the signal separators 118 to 121 and inputs them to the video path unit 127, the audio level detector 123, the audio path unit 124 and the control signal processor 130.
The audio level detector 123 outputs an information indicative of a terminal which outputs the highest level input voice to the video control unit 132. The video control unit 132 outputs, among the video signals collected by the video path unit 127 through the input video signal line 125 from the respective terminals, the video signal of the video conference terminal 102 whose audio level is detected by the audio level detector 123 as the highest to the output video signal line 128.
That is, there is a talker at the video conference terminal which outputs the highest level input voice. The information indicative of the video conference terminal having the talker is output to the video control unit 132. In response to the information, the video control unit 132 instructs the video path unit 127 to select the output video signals of other video conference terminals than that whose audio level is the highest or all of the video conference terminals as input video signals of the video conference terminal having the highest audio level.
In response to the instruction from the video control unit 132, the video path unit 127 selects, among the input video signals, output video signals corresponding to the respective video conference terminals 102 to 105 such that images of the video conference terminals having speakers become the output images of the other video conference terminals than the video conference terminals having talkers and the previously selected images or images of the video conference terminals having speakers become the output images of the video conference terminals having talkers and outputs them to the signal separators 118 to 121 through the output video signal line 128.
The audio signals received by the audio path unit 124 are synthesized to output audio signals corresponding to the respective video conference terminals 102 to 105 by audio signal summation such that voices from all of the other video conference terminals than one video conference terminal can be heard by the one video conference terminal usually, and the synthesized audio signals are output to the signal separators 118 to 121 through the output audio signal line 125.
Then, the respective signal separators 118 to 121 compress and multiplex the output video signals from the video path unit 127 and the output audio signals from the audio path unit 124 and send them to the corresponding video conference terminals 102 to 105 through the bi-directional digital transmission paths 106 to 109.
The interface units 110 of the respective video conference terminals 102 to 105 (FIG. 2) receive the multiplexed output signals sent from the video conference communication controller 101. The received signals are separated to the output video signals and the output audio signals by the signal processor 111. These output video signals and the output audio signals are expanded and then output to the respective displays 115 and the loud speakers 113.
When the privacy communication is to be performed in such conventional video conference system, the video conference communication controller 101 controls, on the basis of an instruction from the controller 116 of the video conference terminal 102 assigning the other video conference terminal of the audio privacy communication, the audio signal obtained in the audio path unit 124 such that voice of the video conference terminal 102 is not sent to other video conference terminals than the assigned specific video conference terminal.
That is, the signals sent out from the respective video conference terminals 102, 103, 104 and 105 as multiplexed signals are separated to the input video signals, the input audio signals and the audio control signals by the respective signal separators 118, 119, 120 and 121. The audio control signals among them are input to the control signal processor 130 through the audio control signal line 129. The control signal processor 130 recognizes the video conference terminal which demands the privacy communication and the other side video conference terminal and sends an information indicative of these video conference terminals to the audio path control unit 131 and the audio level detector 123.
The audio path control unit 131 sends an instruction with which voice of the video conference terminal which assigns the other video conference terminal for the audio privacy communication is sent to only the assigned video conference terminal, voice of the assigned video conference terminal is not sent to other video conference terminals than the assigning video conference terminal and the two video conference terminals between which the audio privacy communication is performed can hear voices from other video conference terminals than the two video conference terminals. In response to such instruction, the audio path unit 124 synthesizes or selects input audio signals supplied through the respective input audio signal lines 122 and sends them to the signal separators 118, 119, 120 and 121 through the respective output signal lines 125 as output audio signals.
Further, the audio level detector 123 receives the instruction related to the audio privacy communication output from the control signal processor 130 and controls the video path unit 127 by supplying the control signal containing the information of the audio privacy communication to the video control unit 132.
That is, the audio level detector 123 detects voice from the input audio signal line 122 having the highest audio level among the input audio signals input through the input audio signal lines 122 excluding the input audio signal of the video conference terminals which perform the audio privacy communication, on the basis of the instruction from the selected video conference terminal (terminal which performs the audio privacy communication) from the control signal processor 130, and transfers the information indicative of the signal separator from which the detected signal is input to the video control unit 132. As a result, the image input from the video conference terminals which are performing the privacy communication is prevented from being displayed on other video conference terminals which are not object of the privacy communication.
As described above, in the conventional multi-point video conference system, the control is performed in the multi-point control unit (video conference communication controller 101) for realizing the privacy communication. However, such conventional multi point video conference system has the following problems.
The first problem is that the general usability of the multi point control unit is lost in the combination of the video conference terminals and the multi-point control unit (video conference communication control unit). That is, in order to realize the privacy communication function in the conventional multi-point video conference system, the multi-point video conference terminals 102, 103, 104 and 105 have to have the controller 116 for providing specific audio control signal corresponding to the control signal processor 130 of the video conference communication controller 101. In other words, it is impossible for the multi-point video conference terminal which outputs such audio control signal to realize the audio privacy communication unless it is combined with the multi-point control unit including the audio communication control unit 131 which operates on the basis of the audio control signals sent from the respective video conference terminals to output an information identifying the video conference terminal which performs the audio privacy communication and the audio path unit 124 for synthesizing voices on the basis of the video conference terminal identifying information from the audio communication control unit 131.
The second problem is that the multi-point video conference system, particularly, the multi-point control unit thereof, is expensive. In general, the multi-point control unit for realizing the multi point video conference is not equipped with the privacy communication function. That is, the multi-point control unit is expensive even when it has no control signal processor and no audio path control unit, etc. As mentioned, in the case where the conventional video conference terminal has to have the privacy communication function, the control signal processor and the audio path control unit, etc., are to be newly added to the multi-point control unit of the multi-point video conference system in order to realize the audio privacy communication. Therefore, in such case, the video conference system becomes more expensive, causing use of such system to be difficult.